Additives for winterization of paraffin inhibitors

ABSTRACT

A winterized paraffin inhibitor, which is capable of being used for preventing the deposition of paraffins in hydrocarbon streams and capable of withstanding freezing or crystallization at freezing or sub-freezing temperatures, may be formed by adding an oxyalkylated branched aliphatic compound having 12 or more carbons to a high molecular weight aliphatic polymer paraffin inhibitor, the oxyalkylated branched aliphatic compound having 12 or more carbons being produced by the oxyalkylation of the branched aliphatic compound having 12 or more carbon atoms in which the branched aliphatic compound having 12 or more carbon atoms is grafted with a polyether via a ring-opening reaction, wherein the polyether is a polymer of ethylene oxide, propylene oxide, butylene oxide, and combinations thereof.

TECHNICAL FIELD

The present invention relates to winterizing additives, and moreparticularly relates to additives for winterizing high molecular weightaliphatic polymer paraffin inhibitors that are used to prevent wax orparaffin deposition in crude oils and other hydrocarbon fluids.

BACKGROUND

Paraffin inhibitors are chemicals used in the production of oil and gasto prevent or minimize the deposition of naturally-occurring paraffinsin crude oils and other produced fluids and to reduce their viscosity inorder to improve flow in the production, transportation, and storage ofthese fluids.

These chemicals are sometimes applied in cold sub-sea conditions, suchas in Canada, in which temperatures range from 0° C. to −40° C.,sometimes even colder. Many paraffin inhibitors used in theseenvironments are composed of high molecular weight aliphatic polymerchains having long chain alkyl moieties, which routinely solidify atsub-zero temperatures. Typically, smaller molecular additives, likemethanol, isopropanol, etc., are used to “winterize” these paraffininhibitors, which means to prevent the freezing or crystallization ofthe paraffin inhibitor during use or storage in freezing or sub-freezingtemperatures. However, it has been shown that the long chain alkylmoiety materials in the paraffin inhibitors are incompatible withalcohols, causing the product to precipitate and lead to solidsformation and phase separation.

Therefore, there is a need for developing winterizing additives that canprevent the freezing or crystallization of high molecular weightaliphatic polymer paraffin inhibitors in sub-zero temperature conditionswithout attendant solids formation or phase separation and that canstabilize these types of paraffin inhibitors for longer term use andstorage at such temperatures.

SUMMARY

There is provided, in one form, a method for winterizing a paraffininhibitor in which an oxyalkylated linear or branched aliphatic compoundhaving 12 or more carbon atoms is introduced into a paraffin inhibitorcomposed of a high molecular weight aliphatic polymer in an effectiveamount to prevent freezing or crystallization of the paraffin inhibitorat temperatures ranging from about 0° C. to −40° C.

There is further provided in another non-limiting form, a winterizedparaffin inhibitor formulation made up of about 1 wt. % to about 70 wt.% of an oxyalkylated branched aliphatic compound having 12 or morecarbons and the remainder being made up of a high molecular weightaliphatic polymer paraffin inhibitor.

In one non-limiting embodiment, the oxyalkylated branched aliphaticcompound is formed by the oxyalkylation of the branched aliphaticcompound having 12 or more carbon atoms in which the branched aliphaticcompound having 12 or more carbon atoms is grafted with a polyether viaa ring-opening reaction, wherein the polyether is a polymer of ethyleneoxide, propylene oxide, butylene oxide, and combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 are photographs illustrating the bottle performance of samples ofa winterized paraffin inhibitor of the kind disclosed herein duringstorage and inversion at −20° C. over a period of 6 to 7 days; and

FIG. 2 is a graphic illustration comparing the viscosity of a highmolecular weight aliphatic polymer paraffin inhibitor to the viscosityof the same paraffin inhibitor containing an oxyalkylated branchedaliphatic winterizing additive of the kind disclosed herein as afunction of temperatures ranging from −23° C. to about 23° C.

DETAILED DESCRIPTION

It has been discovered that an oxyalkylated branched aliphatic compoundhaving 12 or more carbon atoms may be applied to high molecular weightaliphatic polymeric paraffin inhibitors, the kinds that are typicallyused to prevent paraffin deposition in hydrocarbon streams found in coldenvironments in which temperatures may range from about 0° C. to −40°C., to form winterized paraffin inhibitors that are better protectedagainst freezing or crystallization during use or storage in thesetemperature conditions.

The high molecular weight aliphatic polymer paraffin inhibitors commonlyinjected into wellbores to prevent the deposition of naturally occurringparaffins founds in produced hydrocarbon streams, such as crude oil,include, but are not limited to, olefin maleic esters, aliphatic olefinmaleic imides, polyol-based polymers, acrylate-based polymers,methacrylate-based polymers, maleate-based polymers, and combinationsthereof. Because of highly aliphatic nature of these compounds, it hasbeen found that introducing winterizing agents that can more easily bedissolved or inserted into or that are soluble with the polymerstructure of the paraffin inhibitor may result in improved winterizationof the paraffin inhibitor, which is to say, improved ability to preventthe freezing or crystallization of the paraffin inhibitor during use orstorage in freezing or sub-freezing temperatures.

In this regard, oxyalkylated linear or branched aliphatic compoundshaving 12 or more carbon atoms have been shown to have stronginteraction with the polymer structure of the highly aliphatic paraffininhibitors that are commonly used to treat crude oils and such at coldtemperatures, making them effective in forming stable, winterizedparaffin inhibitor formulations. More specifically, the aliphatic natureof the oxyalkylated linear or branched aliphatic compounds renders thesemolecules “soluble” with the polymer matrix of the paraffin inhibitorswhile the grafted ethylene-oxide and/or propylene oxide polymer moietiesof these molecules confer steric hindrance, factors that can helpprevent crystallization and promote pourability or flowability atsub-freezing temperatures.

In a non-limiting embodiment, the backbone of the oxyalkylated linear orbranched aliphatic compound winterizing agent comprises a branchedaliphatic compound having 12 or more carbon atoms. The branches of thealiphatic chain may be composed functional groups made up of 2 to 28carbon atoms each. The branches may have different carbon numbers fromeach other. Examples of such functional groups include, but are notlimited to, alkyl groups having 2 to 28 carbon atoms, arylalkyl groupshaving 2 to 28 carbon atoms, cycloalkyl groups having 2 to 28 carbonatoms, and combinations thereof. In the case of long-chain branchedaliphatic compounds, the compounds may additionally, or in thealternative, comprise branches having functional groups selected fromthe group consisting of oxygen functional groups, nitrogen functionalgroups, sulfur functional groups, phosphorous functional groups, andcombinations thereof. In one non-restrictive embodiment, the branchedaliphatic compound may be crosslinked with one or more other branchedaliphatic compound to give a dendrimer or hyperbranched aliphaticcompound. It is appreciated by one of ordinary skill in the art that ahyperbranched aliphatic may have a random or defined hierarchicalstructure. A dendrimer may be considered to be a hyperbranched aliphaticcompound with a defined hierarchical structure.

The oxyalkylated branched aliphatic compound winterizing agent isproduced by oxyalkylating the branched aliphatic compound having 12 ormore carbon atoms, which involves grafting the branched aliphaticcompound having 12 or more carbon atoms with a polyether. The polyethersthat may be grafted upon the long chain branched aliphatic compoundinclude, without limitation, polymers of ethylene oxide (“EO”), polymersof propylene oxide (“PO”), polymers of butylene oxide, and combinationsthereof. These polymers may be random polymers, block polymers orcombinations thereof. The polyether-grafted branched aliphatic compoundmay be formed through a crosslinking reaction involving an epoxideopening to achieve the desired architecture. The crosslinking reactionmay be base-catalyzed, acid-catalyzed, or uncatalyzed. The crosslinkersuseful in forming the polyether-grafted branched aliphatic compound mayinclude one or more of the following: an epoxide, an isocyanate, acarboxylic acid, an acyl halide, an aldehyde, a nitrile, a halide, anester, an anhydride, an alcohol, an amine, and an amide. Thus, in somenon-limiting embodiments, the oxyalkylation of the branched aliphaticcompound comprises grafting the branched aliphatic compound with apolyether via a ring-opening reaction.

In another non-limiting embodiment, the oxyalkylated branched aliphaticcompound winterizing agent having 12 or more carbon atoms that is formedby the oxyalkylating reaction described in the previous paragraph may bepost-functionalized with a sulfate, sulfonate, phosphate, phosphonate,and/or other such charged species.

Upon the producing the oxyalkylated branched aliphatic compoundwinterizing agent having 12 or more carbon atoms, it may be combinedwith, applied to, or introduced to one or more of the high molecularweight aliphatic polymer paraffin inhibitors disclosed herein to form awinterized paraffin inhibitor formulation. In this formulation, theoxyalkylated branched aliphatic compound winterizing agent having 12 ormore carbon atoms may be present in an amount ranging from about 1 wt. %independently to about 70 wt. %, alternatively from about 10 wt. %independently to about 50 wt. %, and in another non-restrictive version,from about 15 wt. % independently to about 30 wt. %, based on totalweight of oxyalkylated branched aliphatic compound and the highmolecular weight aliphatic polymer paraffin inhibitor. As used hereinwith respect to a range, “independently” means that any threshold givenmay be used together with any other threshold given to provide asuitable alternative range.

In one non-limiting embodiment, the winterized paraffin inhibitorformulation described herein has a viscosity ranging from about 5 cP toabout 60 cP at a temperature of from about 25° C. independently to about−20° C.; alternatively from about −10° C. independently to about −30°C.; and in another non-limiting embodiment at around −20° C. In onenon-limiting embodiment the viscosity of the formulation ranges fromabout 5 cP at room temperature (defined herein as 25° C.) to about 60 cPat low temperature, where “low temperature” is defined herein as any ofthe ranges below room temperature given above.

Once formed, the winterized paraffin formulation described herein may bestored, or may be introduced into a wellbore to interact with ahydrocarbon stream containing paraffins to inhibit or prevent thedeposition of paraffins in the stream. Examples of such streams in theoilfield environment include, but are not limited to, crude oil, aproduction fluid, and combinations thereof. In a non-limitingembodiment, the effective amount of the winterized paraffin formulationthat may be introduced to the stream for purposes of inhibiting paraffindeposition ranges from about 10 ppm independently to about 10,000 ppm,or from about 100 ppm independently to about 1000 ppm, based on thetotal volume of the stream.

A goal of the forming the winterized paraffin inhibitor formulation bycombining the oxyalkylated branched aliphatic compound winterizing agenthaving 12 or more carbon atoms with a high molecular weight aliphaticpolymer paraffin inhibitors is to produce a winterized paraffininhibitor that can withstand freezing or crystallization during use orstorage in freezing and/or sub-freezing conditions and that can be usedto effectively prevent or inhibit deposition of paraffins in hydrocarbonstreams paraffins in an environment in which the temperature ranges fromabout 0° C. to −40° C. For purposes of this disclosure, the term“prevent” and “inhibit” are used synonymously and are both defined tomean “stop.” While complete prevention of freezing or crystallization orcomplete inhibition of paraffin deposition is desirable, it should beappreciated that complete prevention or inhibition is not necessary forthe methods and additives discussed herein to be considered effective.

It can be appreciated that other, optional additives may also be addedto the crude oil stream. These optional additives may include, but arenot necessarily limited to, coagulants, flocculants, corrosioninhibitors, viscosity reducers, winterizing agents different from theoxyalkylated linear or branched aliphatic compound, friction reducers,scale inhibitors, scale dissolvers, paraffin inhibitors, pour pointdepressants, asphaltene inhibitors, clay swelling inhibitors, biocides,antifoulants, flow back aids, surfactants, and combinations thereof. Inone non-limiting embodiment, the oxyalkylated branched aliphaticcompound may be combined with other winterization agents including, butnot necessarily limited to, alcohols, alkylated naphthalenes, polyalkylmethacrylates, chlorinated wax, styrene ester copolymers, and the like.

The invention will be further described with respect to the followingExamples, which are not meant to limit the invention, but rather tofurther illustrate some embodiments.

EXAMPLES Example 1

In FIG. 1, multiple samples of a winterized paraffin inhibitorformulation containing 71.4 wt. % of a maleic olefin ester basedparaffin inhibitor 1 and 28.6 wt. % of a C20+ oxyalkylated aliphatic(“Additive”) were stored and inverted in clear bottles at a temperatureof −20° C. over the course of 6-7 days to evaluate the long termstability of these winterized paraffin inhibitor formulations. Thephotographs of the bottles with the samples inside show that theformulations do not form solids and are completely flowing when storedat −20° C. for longer periods of time. And, when cycled, theformulations consistently returned to their original clear phase.

Example 2

In addition to these tests, the properties, conditions, and inhibitioneffectiveness of a sample of the maleic olefin ester based paraffininhibitor 1 without Additive were compared to the properties,conditions, and inhibition effectiveness of a sample of the maleicolefin ester based paraffin inhibitor 1 with the C20+ oxyalkylatedaliphatic additive.

FIG. 2 shows that the viscosity of maleic olefin ester based paraffininhibitor 1 with the C20+ oxyalkylated aliphatic additive was 10 timesless at −20° C. than the viscosity of the non-winterized maleic olefinester based paraffin inhibitor 1.

Example 3

Finally, Table I below shows the “cold finger test” performance resultsof a sample of maleic olefin ester based paraffin inhibitor 1 with andwithout the additive in waxy crude oil. The Low Shear Wax Deposition(i.e. cold finger) procedure is used to screen paraffin inhibitors inwaxy crude oils. The test unit consists of two main parts. A water bathchamber that keeps the oil at prescribed temperature (usually above theoil's wax appearance temperature) and a metal tube (the cold finger)through which cold fluid circulates, maintaining the finger temperaturebelow that of the surrounding oil. The data in Table I show that thewinterized formulation, the one with the Additive, performed slightlybetter at inhibiting paraffin deposition than the paraffin inhibitor byitself.

TABLE I Cold Finger Test of Maleic Olefin Ester Based Paraffin Inhibitor1 Alone as Compared to Formulation Containing the Additive ProductDeposit Inhibition (%) Maleic olefin ester based paraffin inhibitor 10.980 44.9% Maleic olefin ester based paraffin inhibitor 0.960 46.1% 1 +C20+ oxyalkylated aliphatic additive

Example 4

In a separate evaluation, a second set of paraffin inhibitor formulationsamples having varying amounts of sulfated C24 oxyalkylated aliphaticwinterization agent and isopropanol were stored at −20° C. for 24 hoursand their flow properties observed.

Table II shows that the samples containing the highest amounts of C20+oxyalkylated aliphatic winterization agent exhibited flowability whilethe other samples began to freeze when stored at −20° C. for 24 hours.

TABLE II Flow Property Evaluation of Maleic Olefin Ester Based ParaffinInhibitor 2 with Varying Amounts of Additive and Isopropanol SulfatedC24 Maleic olefin oxyalkylated ester based aliphatic paraffinwinterization inhibitor 2 agent 1 Isopropanol Observation 80 6.6 13.4Slushy 66.7 5.5 27.7 Slushy 50 16.5 33.5 Flowing Sulfated C24 Maleicolefin oxyalkylated ester based aliphatic paraffin winterizationinhibitor 2 agent 2 Isopropanol Observation 80 6.6 13.4 Slushy 66.7 5.527.7 Slushy 62.5 12.4 25.1 Flowing Sulfated C24 Maleic olefinoxyalkylated ester based aliphatic paraffin winterization inhibitor 2agent 3 Isopropanol Observation 80 6.6 13.4 Slushy 66.7 5.5 27.7 Slushy62.5 12.4 25.1 Flowing

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. However, it will be evidentthat various modifications and changes can be made thereto withoutdeparting from the broader spirit or scope of the invention as set forthin the appended claims. Accordingly, the specification is to be regardedin an illustrative rather than a restrictive sense. For example, uses,reactions, paraffin inhibitors, branched aliphatic compounds, functionalgroups, crosslinkers, streams, compositions, proportions, and amountsnot specifically identified or described in this disclosure or notevaluated in a particular Example are still expected to be within thescope of this invention.

The present invention may suitably comprise, consist or consistessentially of the elements disclosed and may be practiced in theabsence of an element not disclosed. For instance, the claims methods orformulation may comprise, consist essentially of, or consist of thesteps or components recited in the independent claims, respectively.More specifically, there may be provided a method for winterizing aparaffin inhibitor, where the method consists essentially of or consistsof introducing an oxyalkylated linear or branched aliphatic compoundhaving 12 or more carbon atoms into a paraffin inhibitor composed of ahigh molecular weight aliphatic polymer in an amount effective tothereby preventing the freezing or crystallization of the paraffininhibitor at temperatures ranging from about 0° C. to −40° C.

There may be further provided a winterized paraffin inhibitorformulation, where the formulation consists essentially of or consistsof an oxyalkylated linear or branched aliphatic compound having 12 ormore carbons and a high molecular weight aliphatic polymer paraffininhibitor wherein the oxyalkylated branched aliphatic compound ispresent in an amount ranging from 1 wt. % to about 70 wt. %, based ontotal weight of oxyalkylated linear or branched aliphatic compound andthe high molecular weight aliphatic polymer paraffin inhibitor.

The words “comprising” and “comprises” as used throughout the claims,are to be interpreted to mean “including but not limited to” and“includes but not limited to”, respectively.

As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise.

As used herein, the term “about” in reference to a given parameter isinclusive of the stated value and has the meaning dictated by thecontext (e.g., it includes the degree of error associated withmeasurement of the given parameter).

As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items.

1. A method for winterizing a paraffin inhibitor, the method comprising:introducing an oxyalkylated linear or branched aliphatic compound having12 or more carbon atoms into a paraffin inhibitor composed of a highmolecular weight aliphatic polymer in an amount effective to therebypreventing the freezing or crystallization of the paraffin inhibitor attemperatures ranging from about 0° C. to −40° C.
 2. The method of claim1, wherein the oxyalkylated linear or branched aliphatic compound isformed by the oxyalkylation of a linear or branched aliphatic compoundhaving 12 or more carbon atoms.
 3. The method of claim 2, wherein thelinear or branched aliphatic compound having 12 or more carbon atoms isa branched aliphatic compound comprising branches containing functionalgroups having 2 to 28 carbon atoms.
 4. The method of claim 3, whereinthe branched aliphatic compound having 12 or more carbon atoms comprisesbranches containing functional groups selected from the group consistingof alkyl groups, arylalkyl groups, cycloalkyl groups, and combinationsthereof.
 5. The method of claim 2, wherein the linear or branchedaliphatic compound having 12 or more carbon atoms is crosslinked toanother branched aliphatic compound to form a hyperbranched aliphaticcompound.
 6. The method of claim 5, wherein the hyperbranched aliphaticcompound is a dendrimer.
 7. The method of claim 2, wherein the linear orbranched aliphatic compound having 12 or more carbon atoms comprisesbranches containing functional groups selected from the group consistingof oxygen functional groups, nitrogen functional groups, sulfurfunctional groups, phosphorous functional groups, and combinationsthereof.
 8. The method of claim 2, wherein the oxyalkylation of thelinear or branched aliphatic compound having 12 or more carbon atomscomprises grafting the linear or branched aliphatic compound having 12or more carbon atoms with a polyether via a ring-opening reaction. 9.The method of claim 8, wherein the polyether is selected from a groupconsisting of a polymer of ethylene oxide, a polymer of propylene oxide,a polymer of butylene oxide, and combinations thereof.
 10. The method ofclaim 1, wherein the paraffin inhibitor composed of a high molecularweight aliphatic polymer is selected from a group consisting of olefinmaleic esters, aliphatic olefin maleic imides, polyol-based polymers,acrylate-based polymers, methacrylate-based polymers, maleate-basedpolymers, and combinations thereof.
 11. The method of claim 1 where theeffective amount of oxyalkylated linear or branched aliphatic compoundranges from 1 wt. % to about 70 wt. %, based on total weight ofoxyalkylated linear or branched aliphatic compound and the highmolecular weight aliphatic polymer paraffin inhibitor.
 12. A winterizedparaffin inhibitor formulation, the formulation comprising: anoxyalkylated linear or branched aliphatic compound having 12 or morecarbons; and a high molecular weight aliphatic polymer paraffininhibitor; wherein the oxyalkylated branched aliphatic compound ispresent in an amount ranging from 1 wt. % to about 70 wt. %, based ontotal weight of oxyalkylated linear or branched aliphatic compound andthe high molecular weight aliphatic polymer paraffin inhibitor.
 13. Thewinterized paraffin inhibitor formulation of claim 12, wherein theformulation is a flowing liquid at a temperature of between about 0° C.and about −40° C.
 14. The winterized paraffin inhibitor formulation ofclaim 12, wherein the linear or branched aliphatic compound is abranched aliphatic compound having 12 or more carbon atoms comprisesbranches containing functional groups selected from the group consistingof alkyl groups having 2 to 28 carbon atoms, arylalkyl groups having 2to 28 carbon atoms, cycloalkyl groups having 2 to 28 carbon atoms,oxygen functional groups, nitrogen functional groups, sulfur functionalgroups, phosphorous functional groups, and combinations thereof.
 15. Thewinterized paraffin inhibitor formulation of claim 14, wherein theoxyalkylation of the branched aliphatic compound having 12 or morecarbon atoms comprises grafting the branched aliphatic compound having12 or more carbon atoms with a polyether via a ring-opening reaction.16. The winterized paraffin inhibitor formulation of claim 15, whereinthe polyether is selected from a group consisting of a polymer ofethylene oxide, a polymer of propylene oxide, a polymer of butyleneoxide, and combinations thereof.
 17. The winterized paraffin inhibitorformulation of claim 12, wherein high molecular weight aliphatic polymerparaffin inhibitor is selected from a group consisting of olefin maleicesters, aliphatic olefin maleic imides, polyol-based polymers,acrylate-based polymers, methacrylate-based polymers, maleate-basedpolymers, and combinations thereof.
 18. The formulation of claim 13,wherein the viscosity of the formulation ranges from about 5 cP at roomtemperature to about 60 cP at a temperature ranging from about −10° C.to about −30° C.
 19. A method for inhibiting paraffin deposition in acrude oil stream containing paraffins, the method comprising:introducing a winterized paraffin inhibitor comprising (1) anoxyalkylated linear or branched aliphatic compound having 20 or morecarbons and (2) a high molecular weight aliphatic polymer paraffininhibitor selected from the group consisting of olefin maleic esters,aliphatic olefin maleic imides, polyol-based polymers, acrylate-basedpolymers, methacrylate-based polymers and/or maleate-based polymers to ahydrocarbon stream containing paraffins in an environment in which thetemperature ranges from about 0° C. to −40° C.; and preventing paraffindeposition within the hydrocarbon stream.
 20. The method of claim 19further comprising adding at least one other additive to the crude oilstream, where the at least one other additive is selected from the groupconsisting of coagulants, flocculants, corrosion inhibitors, viscosityreducers, winterizing agents different from the oxyalkylated linear orbranched aliphatic compound, friction reducers, scale inhibitors, scaledissolvers, paraffin inhibitors, pour point depressants, asphalteneinhibitors, clay swelling inhibitors, biocides, antifoulants, flow backaids, surfactants, and combinations thereof.